This is the smartest staircase ever. (The picture on the left is looking up, the one on the right is looking down- just in case it’s confusing)

via apartmenttherapy.com:
“Limited by space, we melded the idea of a staircase with our client’s desire for a
library to form a ‘library staircase’ in which English oak stair treads
and shelves are both completely lined with books.”- Tim Sloan, Levitate Architects